Despite losing the seat by just 103 votes at last year's general election and although the Tories are allegedly holding back their campaign at David Cameron's request, Nick Clegg's party trails by 17 points in two separate surveys of voters in the key marginal. It will be seen as a resounding thumbs-down to the Lib Dems' role in the Conservative-led coalition government.

A poll of 1,500 voters in the constituency published in a Sunday newspaper put Labour on 46%, the Lib Dems on 29% and the Conservatives on 15%. Its findings were mirrored by an ICM poll for another newspaper that gave Labour a 44% to 27% lead over the Lib Dems – with the Tories' Kashif Ali on 18%. Of voters in the constituency who say they are switching to Labour, 28% blame disaffection with the Lib Dems' role in the coalition, notably over their election pledge-defying support for a rise in tuition fees, the polls reveal.

Labour blitzed the constituency with 500 campaigners yesterday as Ed Miliband made a new overture to disgruntled Lib Dems. The Labour leader urged people to "send a message about the betrayal on fees". Portraying the Lib Dems as locked into a Tory agenda that many do not support, he added: "For the first time since this Conservative-led government was formed, voters will have their chance to pass judgment on David Cameron and Nick Clegg. They can show the government what they feel about police cuts both here and across the country. And they can make clear their anger about a VAT rise that is the wrong tax at the wrong time."

The Lib Dems had won a legal bid to have Labour victor Phil Woolas stripped of the seat. Labour's Debbie Abrahams is now the clear favourite to win Thursday's crucial vote.